Electrical discharge machine with a management information display function

ABSTRACT

A wire cutting electric discharge machine having a first and second group of expendable components, the first group of components being continuously used during machining including the upper and lower wire guides, the upper and lower wire feeders, the filter, and the ion exchange resin of the ion exchanger. The second group of expendable components includes a cutter for wire cutting, and the conveyor belts. At the end of a process involving cutting of the wire and wire extension, the cumulative frequency of use is compared to determine whether the life of the first group of components has terminated. At the end of machining, the CPU compares the working period of each of the second group of components obtained by adding the electric discharge machining time to the cumulative working period before the start of the machining, with an allowable working period read from a management table, to determine whether the life of each component in the second group has terminated. The CPU turns on LEDs which correspond to the exhausted component and that a first or second tanks of a machining fluid supplying device whose water level is lowered, thereby giving an alarm.

TECHNICAL FIELD

The present invention relates to an electrical discharge machine with amanagement information indicating function, and more particularly, to anelectrical discharge machine in which expendable parts can be replacedat an appropriate time and a drop of the machining fluid storage levelcan be quickly coped with.

BACKGROUND ART

If an electrical discharge machine is operated for a long period oftime, various expendable parts of the electrical discharge machine wearaway and suffer deterioration in performance, thus possibly entailing atrouble which disables operation, as well as reduction in machiningaccuracy and machining speed. Accordingly, the exhausted parts must bereplaced with new ones. Conventionally, an operator determines whetherthe life of each expendable part has terminated, on the basis of visualobservation or experience. It is difficult, therefore, to replace eachpart at an appropriate time. If the time for the part replacement is tooearly, the operation cost of the electrical discharge machine increases.If the time is too late, on the other hand, the aforesaid awkwardsituation is entailed.

Further, the electrical discharge machine supplies a machining fluid topredetermined regions, such as the gap between a workpiece and anelectrode, a workpiece stand, etc., by injection, thereby removing heatand machining chips produced during electrical discharge machining. Ifthe machining fluid storage level in a machining fluid reservoirextraordinarily drops due to anything unusual in a machining fluidsupplying device or the like, however, the machining fluid cannot benormally supplied, so that the operation of the electrical dischargemachine is hindered.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide an electricaldischarge machine capable of indicating a termination of the life ofexpendable parts, thereby rationalizing the time for replacement, andpreferably also indicating an extraordinary drop of the machining fluidstorage level, whereby the drop of the machining fluid storage level canbe quickly coped with.

In order to achieve the above object, according to the presentinvention, there is provided an electrical discharge machine with amanagement information indicating function, the electrical dischargemachine having at least one of first and second part groups, the firstpart group including at least one expendable part continually usedduring electrical discharge machining, the second part group includingat least one expendable part used as required during the operation ofthe electrical discharge machine.

This electrical discharge machine comprises: detecting means forexecuting detection of the working period of the at least one expendablepart, included in the first part group, during the time interval betweenthe start of the electrical discharge machining and a firstpredetermined point of time, and/or detection of the frequency of use ofthe at least one expendable part, included in the second part group,during the time interval between the start of operation of theelectrical discharge machine and a second predetermined point of time;updating means for updating a corresponding one of the cumulativeworking period and the cumulative frequency of use of each of theexpendable parts in accordance with a corresponding one of the workingperiod and the frequency of use thus detected; discriminating means formaking comparison between the updated cumulative working period and theallowable working period of the expendable part and/or comparisonbetween the updated cumulative frequency of use and the allowablefrequency of use of the expendable part, thereby determining whether thelife of each of the expendable parts has terminated; and indicatingmeans for indicating a termination of the life of each of the expendableparts in accordance with the result of determination by thediscriminating means.

Preferably, the electrical discharge machine includes a machining fluidsupplying device having a machining fluid reservoir and adapted tosupply a machining fluid to a predetermined region of the electricaldischarge machine, and second detecting means for detecting the storagelevel of the machining fluid in the machining fluid reservoir, thediscriminating means compares the machining fluid storage level thusdetected and a predetermined level, and the indicating means indicatesan extraordinary drop of the machining fluid storage level in accordancewith the result of the comparison.

According to the present invention, as described above, a termination ofthe at least one expendable part of the electrical discharge machine isindicated when the cumulative working period or the cumulative frequencyof use of this part, updated in accordance with the working period ofthe part detected during the time interval between the start of theelectrical discharge machining and the first predetermined point of timeor the frequency of use during the time interval between the start ofoperation of the electrical discharge machine and the secondpredetermined point of time, attains the allowable working period or theallowable frequency of use of the part. Accordingly, an operator canproperly judge the time for the replacement of the expendable partwithout any visual observation or experience. Thus, lowering of theelectrical discharge machining accuracy attributable toinappropriateness of the time for the part replacement, occurrence oftrouble in the electrical discharge machine, etc. can be prevented, andthe operation cost of the electrical discharge machine can be reduced.Since the extraordinary drop of the machining fluid storage level ispreferably indicated, the operator can quickly take a necessary measureto meet the situation, so that the operation of the electrical dischargemachine cannot be hindered by the extraordinary drop of the machiningfluid storage level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the principal part of a wire-cutelectrical discharge machine with a management information indicatingfunction according to one embodiment of the present invention;

FIG. 2 is a schematic sectional view showing water level detectorsattached to the electrical discharge machine of FIG. 1 and theirperipheral elements, in which the stored water level of a first tank islowered,

FIG. 3 is a schematic view similar to FIG. 2, showing a state in whichthe stored water level of a second tank is lowered;

FIG. 4 is a diagram showing a management table stored in a random accessmemory shown in FIG. 1;

FIG. 5 is a flow chart showing the first half of a control programexecuted by a central processing unit shown in FIG. 1; and

FIG. 6 is a flow chart showing the second half of the control program ofFIG. 5.

BEST MODE OF CARRYING OUT THE INVENTION

Referring to FIG. 1, a wire-cut electrical discharge machine accordingto one embodiment of the present invention comprises a conventionalmachine body 2. The machine body 2 is provided with a table (not shown)movable within a horizontal plane, and a workpiece stand for carrying aworkpiece and a machining fluid pan surrounding the same are fixed tothe top surface of the table. Further, the machine body 2 is providedwith a conventional wire transportation device, which includes upper andlower wire guides, a guide roller, a motor, a pair of feed rollers, anda pair of conveyor belts, and a conventional automatic wire extensiondevice including a cutter for wire cutting. While executing electricaldischarge machining, the machine body 2 transports a wire electrode to awire recovery box, along a wire transportation path which extendsthrough nozzles attached individually to the upper and lower wireguides, and drives the cutter for wire cutting and the like of the wireextension device, thereby automatically effecting wire extension. Themachine body 2 is further provided with an electrical dischargemachining power source unit (not shown), and a voltage from this powersource unit is applied to the wire through upper and lower feeders sothat electric discharge is caused in the gap between the workpiece andthe wire.

Also, the electrical discharge machine comprises a machining fluidsupplying device for supplying a machining fluid to a predeterminedregion of the machine body 2, e.g., the electric discharge gap. Thisdevice includes a machining fluid reservoir which is composed of a firsttank 4 for storing clean water as the machining fluid and a second tank3 for storing contaminated water, whereby clean water is supplied from awater main to the first tank 4. A strainer and a filter, used to removeimpurities contained in the contaminated water, are interposed betweenthe two tanks 3 and 4. An ion exchanger for adjusting the electricalconductance of the clean water as the machining fluid is attached to thefirst tank 4, and the peripheral wall of the second tank 3 is providedwith a machining fluid discharge port which is located below the upperedge of a partition wall dividing the two tanks, with respect to thedirection of the height of the device. The tanks 3 and 4 are providedwith water level detectors 5 and 6, respectively, each having one endfixed to the peripheral wall of the tank and a free end attached to afloat 5a or 6a.

Further, the electrical discharge machine comprises a numerical controldevice (hereinafter referred to as NC device) 1 for controlling theoperation of the machine body 2, and the NC device includes a centralprocessing unit (hereinafter referred to as CPU) 10. The CPU 10 isconnected, by means of a bus 19, with a read-only memory (ROM) 11 storedwith an NC device control program, and a nonvolatile random accessmemory (RAM) 12 of a battery-backup type for storing a machining programand a table for part life management (hereinafter referred to asmanagement table) 20 which will be mentioned later with reference toFIG. 4.

In the present embodiment, expendable parts to be subjected to lifemanagement include a first part group composed of parts individuallycontinually used during the electrical discharge machining and a secondpart group composed of parts individually used as required during theelectrical discharge machining. The first expendable part group includesthe upper and lower wire guides, the upper and lower feeders, the filterand the strainer for machining fluid filtration, and ion exchange resinof the ion exchanger. The second expendable part group, on the otherhand, includes the cutter for wire cutting and the belts of theautomatic wire extension device. As shown in FIG. 4, the managementtable 20 has first to fourth memory regions for storing managementitems, including part names, initial values, variables, and liferetention/end indicating information, fifth to eleventh memory regionsfor storing the names of the aforesaid seven expendable parts as objectsof management, twelfth to eighteenth memory regions for storing initialvalues TA(1) to TA(7) individually indicating the life performance ofthe aforesaid various parts, that is, the allowable working period ofthe parts included in the first part group and the allowable frequencyof use of the parts included in the second part group, nineteenth totwenty-fifth memory regions for storing variables T(1) to T(7)individually indicating the cumulative working period of the partsincluded in the first part group and the cumulative frequency of use ofthe parts included in the second part group, and twenty-sixth tothirty-second memory regions for storing data S(1) to S(7) indicatingwhether the life of each part has terminated. For example, the initialvalues TA(1) to TA(7) are adjusted to values for the time of delivery ofthe electrical discharge machine, while the variables T(1) to T(7) arereset to the value "0" at the time of delivery of the electricaldischarge machine and at the time of replacement of their correspondingexpendable parts.

Further, the CPU 10 is connected, by means of the bus 19, with a servocircuit 13 for controlling the drive of servomotors for various axes inthe machine body 2, an interface 14 connected with various sensors inthe machine body 2, the water level detectors 5 and 6, etc., a tapereader 15 for reading the machining program from a tape, a manual datainput device 16 with CRT display (hereinafter referred to as CRT/MDI),and a machine control panel 17 for operating the NC device and settingvarious conditions including electrical discharge machining conditions.Furthermore, the CPU 10 is connected, by means of the bus 19, withindicating means 18 which, including a required number of light emittingdiodes, is used to indicate a termination of the life of the expendableparts and an extraordinary drop of the machining fluid storage level.

Referring now to FIGS. 5 and 6, the operation of the electricaldischarge machine with the aforementioned construction will bedescribed.

If an operator inputs a command for the start of electrical dischargemachining through the machine control panel 17 after connecting theelectrical discharge machine to the power supply, the CPU 10 restarts atimer contained therein, and then periodically executes the controlprogram shown in FIGS. 5 and 6.

First, the CPU 10 reads a first block (in general, one machining programblock) of the machining program from the tape reader 15 or the RAM 12(Step 100), and determines whether a wire cut/removal command M50 forautomatic wire extension is described in this block (Step 101). If theresult of determination in this step is negative, whether a wireextension command M60 is described in the block read in Step 100 isdetermined (Step 102). If the result of determination in this step isnegative, whether a command M02 indicative of an end of the machiningprogram is described is determined (Step 103). If the results ofdetermination in Steps 101 to 103 are all negative, a required processis executed in accordance with the command described in the block readin Step 100 (Step 104), whereupon the program of FIGS. 5 and 6 for thepresent control program execution period (hereinafter referred to ascontrol period) is finished.

If the result of determination in Step 101 for a subsequent controlperiod is positive, that is, if the wire cut/removal command M50 isread, the electrical discharge machine executes a wire cut/removalprocess (Step 105). Namely, after the execution of the electricaldischarge machining and the supply of the machining fluid are stoppedindividually, the wire is cut by means of the cutter, and the pairedbelts of the wire transportation device are then driven to throw a cutwire half portion on the lower-course side, with respect to the cutter,into the wire recovery box.

Then, the CPU 10 adjusts an index N, indicative of an expendable partname, to the value "6" which represents the cutter for wire cutting(Step 106). As a result, the twenty-fourth memory region of themanagement table 20, stored with the variable T(6), is addressed, andthe variable T(6) is read from the management table 20, although adetailed explanation is omitted herein. Seeing that the cutter has beenused once in the aforesaid wire cutting process, the CPU 10 adds thevalue "1" to the variable T(6), thereby updating the variable to a valueindicative of the cumulative frequency of use of the cutter after thewire cutting process, and the variable T(6) thus updated is then storedin the aforesaid memory region (Step 107). Then, the initial value TA(6)indicative of the allowable frequency of use of the cutter and theupdated variable T(6) indicative of the cumulative frequency of use ofthe cutter, read from the seventeenth and twenty-fourth memory regionsof the management table 20, respectively, are compared to determinewhether the cutter life has terminated (Step 108). If the result ofdetermination in this step is positive, the life retention/endindicating data S(6) of the value "1," indicative of a termination ofthe cutter life, is written in the thirty-first memory region of themanagement table 20, and a required output signal is delivered to theindicating means 18 to turn on that one of the light emitting diodeswhich corresponds to the cutter, thereby warning of the termination ofthe cutter life (Step 109), whereupon the program proceeds to Step 110.If the result of determination in Step 108 is negative, on the otherhand, the program proceeds directly from Step 108 to Step 110 withoutgoing through Step 109.

After the value "1" is added to the index N to update the index N to thevalue "7" in Step 110, whether the index N is equal to the value "8" isdetermined (Step 111). Since the result of determination in this step isnegative, the value "1" is added to the variable T(7) indicative of thecumulative frequency of use of the paired belts of the wiretransportation device, in view of the fact that the paired belts havebeen used once in the wire removal process, whereby the variable T(7) isupdated to a value indicative of the cumulative frequency of use of thebelts after the wire removal process in Step 105 (Step 107). Thevariable T(7) thus updated is stored in the thirty-second memory regionof the management table 20, and this variable and the initial valueTA(7), indicative of the allowable frequency of use of the belts andread from the eighteenth memory region, are compared to determinewhether the life of the belts has terminated (Step 108). If the resultof determination in this step is positive, the data S(7) for the value"1," indicative of a termination of the belt life, is written in thethirty-second memory region of the management table 20, and acorresponding light emitting diode of the indicating means 18 is turnedon the warn of the termination of the belt life (Step 109), whereuponthe program proceeds to Step 110 mentioned before. If the result ofdetermination in Step 108 is negative, the program proceeds directlyfrom this step to Step 110. Subsequently, the index N is updated to thevalue "8" in Step 110, so that the result of determination in Step 111is positive, and the program proceeds to Step 102. In the control periodduring which the wire cut/removal process is executed, the results ofdetermination in Step 102 and Step 103 subsequent thereto are bothnegative, so that the program proceeds to Step 104. In this case, thewire cut/removal process is already executed, so that the execution ofthe program for the present control period is finished without executingany substantial processing in Step 104.

If the aforesaid wire cut/removal process is executed, a machiningprogram block including the wire extension command M60 is read in Step100 for a subsequent control period, so that the result of determinationin Step 112 for this control period is positive. In this case, a wireextension process is executed in Step 112. More specifically, the wirestretched between the upper and lower wire guides by the operation ofthe wire extension device is fed between the paired belts of the wiretransportation device which are located on the lower-course side of thelower wire guide. Then, the wire held between the two belts is fedthereby between a pair of feed rollers arranged on the lower-course sideof the belt pair. As the paired rollers rotate, the wire reaches thewire recovery box. When the wire stretch process is finished in thismanner, the paired belts are driven in directions to recede from eachother, so that the wire is disengaged from the belt pair.

When the wire extension process in Step 112 is finished, the CPU 10,seeing that the belt pair has been used once in the wire extensionprocess, adds the value "1" to the variable T(7) indicative of thecumulative frequency of use of the belts, thereby updating this variable(Step 113), and then executes Step 114 corresponding to Step 108 for theaforesaid determination, thereby determining whether the life of thebelt pair has terminated. If necessary, moreover, the CPU 10 executesStep 115 corresponding to Step 109 for the aforesaid alarm indication,thereby turning on a corresponding one of the light emitting diodes incase of a termination of the life of the belt pair. Thereupon, theexecution of the program for the present control period is finished.

When the wire extension is finished in this manner, regular electricaldischarge machining is executed. During the electrical dischargemachining, the CPU 10 periodically executes the control program of FIGS.5 and 6.

If it is concluded that a program end command M20 is included in themachining program block read in Step 100 for a subsequent control period(Step 103), the CPU 10 stops the aforesaid timer and sets the index N to"1" (Steps 116 and 117), and reads the variable T(1), indicative of thecumulative working period of the wire guides before the start of thepresent cycle of electrical discharge machining, from the nineteenthmemory region of the management table 20 which corresponds to the indexN (=1). Seeing that the wire guides have been continually used duringthe electrical discharge machining, the CPU 10 adds the presentelectrical discharge machining execution time T, metered by means of thetimer, to the variable T(1), thereby updating this variable to a valueindicative of the cumulative working period of the wire guides beforethe end of the present cycle of electrical discharge machining (Step118). In Step 118 corresponding to Steps 108 and 114 for the aforesaiddetermination, the allowable wire guide working period and the updatedcumulative wire guide working period are compared to determine whetherthe life of the wire guides has terminated. If necessary, moreover, Step120 corresponding to Steps 109 and 115 for the aforesaid alarmindication is executed. In case of a termination of the life of the wireguides, the data S(1) of the value "1," indicative of the termination ofthe wire guide life, is written in the twentieth memory region of themanagement table 20, and a corresponding one of the light emittingdiodes is turned on.

Subsequently, in Step 121, whether the index N is equal to the value "5"is determined. Since the result of determination in this step isnegative, the value "1" is added to the index N in Step 122. Thereafter,the program returns to Step 118 described above, whereupon a series ofprocesses, including Step 119 for the life discrimination, Step 120 forthe alarm indication, Step 121 for the index value discrimination, andStep 122 for the index renewal, is repeatedly executed until the index Nattains the value "5." Thereupon, whether the respective lives of thefeeders, filter, strainer, and ion exchanger have terminated isdetermined. If it is concluded that the life of any of these expendableparts has terminated, a corresponding one of the light emitting diodesof the indicating means 18 is turned on.

If any of the light emitting diodes is turned on in this manner, theoperator can easily ascertain the time of termination of the life of thecorresponding expendable part, that is, the time for replacement. Afterreplacing this part, the operator operates the machine control panel 17,thereby causing the same to write a variable of the value "0,"indicative of the virginity of a replacing part, in a corresponding oneof the nineteenth to twenty-fifth memory regions of the management table20, and to write part life retention/end indicating data of the value"0," indicative of the retention of the life of the replacing part, in acorresponding one of the twenty-sixth to thirty-second memory regions ofthe management table 20. If the allowable working period or allowablefrequency of use of the replacing part is different from that of thereplaced one, the initial value stored in a corresponding one of thetwelfth to eighteenth memory regions of the management table 20 isupdated to a required value.

If data of the value "1," indicative of the end of the part life, isstored in any of the twenty-sixth to thirty-second memory regions of themanagement table 20 during the preceding cycle of electrical dischargemachining, the CPU 10 turns on the light emitting diode corresponding tothe exhausted part at the time of connecting the electrical dischargemachine to the power supply, although an illustration and a detaileddescription are omitted herein.

If the circulation of the machining fluid (water) in the machining fluidsupplying device or between the machining fluid supplying device and theelectrical discharge machine body 2 gets out of order, the water levelin the first tank 4 becomes much lower than the water level in thesecond tank 3, as shown in FIG. 2. If the machining fluid is in shortsupply, moreover, the water level in the second tank 3 becomes muchlower than the water level in the first tank 4, as shown in FIG. 3. Ifthe water level in either tank drops thus extraordinarily below apredetermined water level, an output signal indicative of a water leveldrop is delivered from a corresponding one of the water level detectors5 and 6. On receiving the output signal of the water level detectorthrough the interface 14, the CPU 10 turns on the light emitting diodecorresponding to the tank suffering the water level drop, therebywarning of the extraordinary water level drop. As a result, the operatorcan quickly cope with the water level drop. The water level detectors 5and 6 may alternatively be connected directly to their correspondinglight emitting diodes so that these light emitting diodes can be turnedon.

The present invention is not limited to the embodiment described above,and various modifications may be effected therein.

For example, although the case in which the present invention is appliedto the wire-cut electrical discharge machine has been described inconnection with the above embodiment, the invention may be applied toelectrical discharge machines of any other types. In the aboveembodiment, moreover, the seven expendable parts including the upper andlower wire guides are regarded as the objects of management. The presentinvention is not limited to this, however, and any other expendableparts, such as bearings, may be included in the objects of management.In the embodiment described above, furthermore, the cumulative workingperiod at the end of electrical discharge machining, obtained by addingthe working period of each expendable part subjected to the electricaldischarge machining to the cumulative working period before the start ofthe electrical discharge machining, is compared with the allowableworking period to determined whether the life of the expendable part hasterminated. Alternatively, however, the same processing may be executedduring the electrical discharge machining. Moreover, whether the life ofeach part has terminated may be determined by obtaining the residualworking period during or at the end of the electrical dischargemachining and the residual frequency of use at the end of the wirecut/removal process by substracting the working period and the frequencyof use associated with the electrical discharge machining and theaforesaid process from the residual working period and the residualfrequency of use at the start of the electrical discharge machining. Inthis case, the allowable working period and the allowable frequency ofuse are set as the residual working period and the residual frequency ofuse, respectively, at the time of delivery of the electrical dischargemachine and at the time of replacement of the parts.

I claim:
 1. In an electrical discharge machine having at least one offirst and second part groups, said first part group including at leastone expendable part continually used during electrical dischargemachining, said second part group including at least one expendable partused as required during the operation of said electrical dischargemachine, the electrical discharge machine with a management informationindicating function comprising:detecting means for executing detectionof a working period of said at least one expendable part, included insaid first part group, during the time interval between start ofelectrical discharge machining and a first predetermined point of time,and/or detection of frequency of use of said at least one expendablepart, included in said second part group, during the time intervalbetween start of operation of said electrical discharge machine and asecond predetermined point of time; updating means for updating acorresponding one of a cumulative working period and a cumulativefrequency of use of each said expendable part in accordance with acorresponding one of the detected working period and the detectedfrequency of use; discriminating means for making comparison betweensaid updated cumulative working period and an allowable working periodof said expendable part and/or comparison between said updatedcumulative frequency of use and an allowable frequency of use of saidexpendable part, thereby determining whether life of each saidexpendable part has terminated; and indicating means for indicating atermination of the life of each said expendable part in accordance withresult of the determination by said discriminating means.
 2. Anelectrical discharge machine with a management information indicatingfunction according to claim 1, wherein said first predetermined point oftime is a time for the end of the electrical discharge machining.
 3. Anelectrical discharge machine with a management information indicatingfunction according to claim 1, wherein said electrical discharge machineincludes a machining fluid supplying device having a machining fluidreservoir and adapted to supply a machining fluid to a predeterminedregion of said electrical discharge machine, and second detecting meansfor detecting a storage level of the machining fluid in said machiningfluid reservoir, said discriminating means compares the machining fluidstorage level thus detected and a predetermined level, and saidindicating means indicates an extraordinary drop of said machining fluidstorage level in accordance with result of the comparison.
 4. Anelectrical discharge machine with a management information indicatingfunction according to claim 2, wherein said electrical discharge machineincludes a machining fluid supplying device having a machining fluidreservoir and adapted to supply a machining fluid to a predeterminedregion of said electrical discharge machine, and second detecting meansfor detecting a storage level of the machining fluid in said machiningfluid reservoir, said discriminating means compares the machining fluidstorage level thus detected and a predetermined level, and saidindicating means indicates an extraordinary drop of said machining fluidstorage level in accordance with result of the comparison.